Kuiper Belt

A region of the outer solar system populated by an estimated ten billion
to one trillion rock-ice bodies known as Kuiper
Belt objects (KBOs). It stretches from about 30 AU
from the Sun (Neptune's distance) to about 50 AU and forms an inner, flattened
extension of the Oort Cloud.

The Kuiper Belt is an older structure than the more spherical outer part
of the Oort Cloud. KBOs formed pretty much in their present locations –
far enough out not to be tossed around by the giant planets – whereas
the more distant Oort cloud objects actually formed closer to the Sun than
KBOs and were then slung into their present huge orbits by gravitational
interactions with Jupiter and the other
gas giants.

The Kuiper Belt is thought to be the source of short-period
comets and of centaurs. It is named
after Gerard Kuiper who predicted its existence
in 1951 but is also sometimes referred to as the Edgeworth-Kuiper
belt, in recognition of the amateur astronomer Kenneth Edgeworth
(1880–1972) who, in his only scientific paper, published in the Journal
of the British Astronomical Association in 1942, was the first to suggest
the existence of a region of comet-like objects beyond the outer planets.

The first observational support for the Kuiper Belt came in 1992 when David
Jewitt of the University of Hawaii and Jane Luu of the University
of California, Berkeley discovered a 200-kilometer-wide object circling
the Sun beyond the orbit of Pluto. Since then,
more such objects have been found. Estimates suggest that as many as 70,000
Kuiper Belt objects with a diameter of more than 100 km may exist in this
region.

Further studies of the Kuiper Belt by telescopes and space probes, such
as New Horizons, will help shed light
on what are extremely primitive remnants from the early accretional phase
of the solar system. See also planetary
systems, formation.